leshner



Feb. 24, 1948. E. LESHNER PLOTTING BOARD AND PROTRACTOR SQUARE FiledMarch 22, 1946 INVENTOR. ErV/n L eg/rner 65 4, fi/VD HTTOC/VEYS PatentedFeb. 24, 1948 PLOTTING BOARD AND PROTRACTOR SQUARE Ervin Leshner,Philadelphia, Pa.

Application March 22, 1946, Serial No. 656,239

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental purposes without payment to me of anyroyalty thereon.

This invention relates to plotting devices and particularly to aprotractor T-square having a novel locking feature.

In using a conventional T-square or a protractor T-square where accuracyis a requirement, the head of the T-square must be kept constantlyagainst the end of the drawing board or have a similar guide. Thisrequires the constant use of one hand, leaving only one hand tomanipulate the pens, pencils or other drafting equipment.

Moreover, for certain kinds of work the blade of a T-square maypreferably be momentarily locked in a fixed position with respect to theboard and, for rapid operation, any locking means which is provided mustnecessarily be operative in minimum time and with minimum effort.

It is therefore an object of this invention to provide a self lockingmeans for a T-square whereby, if the free end of the blade is raisedvery slightly from the face of the board when about to move it on theboard from one place to another, the T-square is automatically unlocked,and when the blade is put flat on the board in a position in which it isto be used, the blade is automatically locked.

Other objects and advantages will be evident when the followingdescription is considered with reference to the drawing, wherein Fig. 1is a top plan view of a fragment of a drawing board and a protractorT-square embodying the principles of my invention;

Fig. 2 is a longitudinal section taken at 2-2 of Fig. 1 through theguide and locking means as it appears when the T-square is in the lockedposition.

Fig. 3 is a view like Fig. 2 except that the locking means is in theunlocked position.

Like reference characters refer to like parts throughout the severalviews.

In the drawing, a drawing board has a channel shaped rail 12 extendingalong one edge and is fastened to the board by screws l4. Additionalguide rails l2 may, of course, be provided for other edges of the boardif so desired.

The T-square has a blade l6 preferably of transparent plastic materialpivotally attached to a sheet metal head l8 by a hinge pin 20. A bolt 22extends through a hole in the blade IB "and through an arcuate slot 24in the head IS. A thumb nut 26 on the bolt 22 clamps the blade and headtogether at any selected angle. The inner edge of the sheet metal headIt is bent downward to form a guide surface l5 for guiding the headalong the upper inner edge of the rail 12, and is curved outward so thatthe end II will 2 bear with considerable pressure against the inside ofthe rail and form a clamp for holding the head it in any desiredposition on the rail 12. The outer edge of the head l8 has a degreegraduation 23 extending from 0 to 60 degrees in either direction fromthe zero position shown. A line 30 on the underside of the blade [6 isalignable with the degree graduation to indicate the angle selected. Theoperation of the device is as follows:

When a line is to be drawn along an edge of the blade it, the blade isallowed to lie fiat on the board 10 as in Fig. 2. In this position theclamping end I! holds the guiding edge l5 tightly against the upper edgeof the rail l2. When the desired line has been drawn and the T-square isto be moved, it is only necessary to tilt the blade as in Fig. 3 wherebythe clamping end I! is withdrawn from the rail l2, permitting the head 3to be moved to the next position. The amount which the blade must betilted to free the head 58 so that it can be moved, is greatlyexaggerated in Fig. 3 for purposes of illustration. A very slight tiltof the blade only will free the head so that it will slide along therail.

While I have shown and described a single exemplification of my improvedplotting board and protractor square, it will be understood that changesmay be made, as for instance changes in the form of the clamping means,without departing from the spirit of the invention, to define which, Iclaim:

1. In combination, a plotting board, a T-square, a channel shaped railsecured to the board along one edge, and a guide and clamping partextending downward from the underside of the head of said T-square intothe channel of said rail, said guide and clamping part bearing tightlynear the top edge of that side of the channel which is nearest the'boardand nearer the bottom on the other side of the channel, whereby saidT-square is locked against movement on said board when said T-squarelies flat on said board and free to move on said board when the outerend of the head of said T-square is tilted downwardly.

2. The device defined in claim 1 wherein the side of the channelfarthest from said board is less in height than the side nearest saidboard.

ERVIN LESHNER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Giehler "a--- Nov. 19. 1929

